Immersion vibrator



July 23, 1957 I s. GlERTZ-HEDSTROM 2,809,309

1 IMMERSION VIBRATOR Filed Sept. 2, 1953 5776 GIEETZ-HEDSZ'EO'IM UnitedStates Patent IMMERSION VIBRATOR I Application-SeptemberZ, 1953,Serial'iNo. 318,129

lclaima. l-252 This invention relates to an immersion vibrator, that isto say, a vibrator Qfthe type intended for immersion at least partiallyin a semi-fluid or. viscous material to be vibrated, such as concrete.

It is already known to employ so-called rod vibrators for this purpose,and numerous types of such rod vibrators are available all consisting ofa longitudinal tubular casing having a rotary vibrating member in theform of an eccentric or the like located therein. In order to producethe greatest possible vibratory effect in the concrete it is necessaryfor the rod vibrator to carry out extensive movements, that is to say,it should have a great vibratory amplitude, but as the stresses thus setup are very considerable it is difficult to obtain this amplitude onaccount of the limited strength of the constructional material.

The present invention has for its object the construction of animmersionvibrator, the active part of which is capable of working with largeamplitudes without subjecting the vibrating element to heavy stresses.According to the invention this is achieved by resiliently connecting arod vibrator of a suitable type with an auxiliary structure or casing,the natural frequency of which is substantially the same as theoperating frequency of the rod vibrator. The connection between theauxiliary structure and the rod vibrator should preferably besymmetrical and resilient and preferably the auxiliary structure orcasing is symmetrically mounted relatively to the rod vibrator proper.

The immersion vibrator according to the invention is hereafter moreparticularly described with reference to the accompanying drawing fromwhich further characteristic features of the invention will be seen.

In the drawing,

Fig. 1 is an axial section through an immersion vibrator according tothe invention, which is primarily intended to illustrate the inventiveprinciple, and

Fig. 2 shows an axial section through another form of construction whichis found preferable in practice.

In Fig. 1, 1 is a rod vibrator of a customary type at the outer end ofwhich a bowlor sleeve-shaped auxiliary structure 2 is attached, freelysurrounding the lower portion of the rod vibrator and connected to thelatter by means of a resilient rod 3 arranged coaxially with the rodvibrator. The auxiliary structure 2, which is so dimensioned relativelyto the rod vibrator that its natural frequency approximately correspondsto the operating frequency of the rod vibrator, is arrangedsymmetrically in relation to the rod vibrator 1. When the rod vibrator 1is started, it is found that the auxiliary structure will vibrate withan appreciably greater amplitude than the rod vibrator. In the idealcase the rod vibrator 1 remains practically stationary or in rest, whilethe auxiliary structure performs a very extensive and powerful movement.If the immersion vibrator 1 shown in Fig. 1 is provided with a flexiblepacking between the upper edge of the auxiliary structure and the casingof the rod vibrator proper 1 so that concrete cannot penetrate into thesleeve 2v 2, said vibrator maybe-employed for vibrating concrete andwill then have a very much greater effect than the rod vibrator-1' byitself.

In the form of construction shown in Fig. 2 the rod vibrator proper 1 isof asomewhat diiferent form to that in. Fig. l but works insubstantially the same manner. In Fig. 2 the, auxiliary structure 2 isgiven the form of a symmetrical tubular casing 4 with a rounded bottom 5Which surrounds the rod vibrator 1 along its whole length. The casing-4,which may be of steel, for example, is concentric with the rod vibratorI and isseparated from thelatter by an annular space 6. A lower-end 1a.of. the rod vibratonl is. Spaced from the casing 4 and may be termed thefree end of therod. vibrator. Attire uppen end of the rod vibrator thecasing isrigidly connected. to the forrner by means of flanges 7 on the.rod

vibrator r e asi g If d s red. a ymmetrical resilient connection, suchas a rubber ring connection, can also be arranged between the rodvibrator and the casing. However, it is to be understood that the lowerportion of the casing due to the resiliency of the casing itself will befree to oscillate relative the rod vibrator proper also without suchresilient connection. In other words, an upper portion 4a of the casing4 may comprise the resilient connection between the rod vibrator 1' andthe lower portion of the casing 4.

As an example of the effect obtainable according to the invention it maybe mentioned that in a practical experiment with a rod vibrator of thetype shown in Fig. 2 but without the auxiliary structure according tothe invention, at a frequency of about 7000 R. P. M. an

amplitude of the rod vibrators outer surface of 0.7 mm. was obtained.When this rod vibrator was subsequently fitted With a resilientauxiliary structure according to Fig. 2 consisting of a steel pipehaving a wall thickness of some millimeters and an external diametercorresponding to approximately twice the diameter of the rod vibratorproper and so chosen that the natural frequency thereof substantiallycorresponded to the operating frequency of the rod vibrator, the doubleamplitude was measured at the auxiliary structure, whilst at the sametime the amplitude of the rod vibrator was reduced below the value of0.7 mm., mentioned above.

The vibrating element in the immersion vibrator according to theinvention may, as already mentioned, be constructed in accordance withpreviously known principles, for example the pendulum principleaccording to the U. S. Patent No. 2,194,410 of March 19, 1940, or in theform of other vibrating rods with eccentric shafts and bearings withoutaffecting the method of operation of the outer tube. As the rod vibratorno longer comes into direct contact with the medium vibrated owing toits surrounding auxiliary structure, it is not necessary to constructthe vibration generator proper as a complete rod vibrator, but avibrating element similar in principle may be employed.

In addition to the increased amplitude obtained by adopting theinventive principle as described above, it is possible to producerelatively light immersion vibrators with a large effective surface,that is to say, a large diameter in practice, without the introductionof heavy masses, and in this way a considerable increase in thevibratory effect is obtained without loading the immersion vibrator andvibratory element unnecessarily.

It is obvious that the forms of construction shown do not limit thepossibilities for applying the inventive principle. Thus, the auxiliarystructure may also consist of a purely axial extension of the rodvibrator, and the resilient connection between the rod vibrator and theauxiliary structure may be obtained by different auxiliary means withinthe scope of the invention. As an example of the latter, reference maybe made to the fact that the casing 4 in Fig. 2 can be constructed witha progressively increasing thickness of material at its upper partnearest to the fixing point, whereby the oscillating movements willexert lower stresses on the casing.

' What I claim is:

1. An immersion vibrator comprising, in combination, a vibrationgenerator including a rod rotatably mounted inan elongated casing, anauxiliary structure adjacent to the generator, said auxiliary structureincluding a casing at least partially surrounding the vibrationgenerator, the

internal surface of said casing being radially spaced from 7 saidvibration generator, and means for resiliently connecting the generatorto the auxiliary structure to permit the auxiliary structure tooscillate independently of the generator, the natural frequency of saidauxiliary structure being substantially the same as the operatingfrequency of the vibrator.

2. An immersion vibrator comprising, in combination, a slender vibrationgenerator having a free end, an auxiliary casing surrounding said freeend of said generator References Cited in the file of this patent UNITEDSTATES PATENTS 2,018,789 Jorgensen Oct. 29, 1935 2,148,722 Baily Feb.28, 1939 2,194,410 Svenson Mar. 19, 1940 2,360,803 Steurman Oct. 17,1944 2,437,983 Wenander Mar. 16, 1948 2,500,293 OConnor Mar. 14, 19502,649,286 Karlstrom Aug. 18, 1953 FOREIGN PATENTS 145,826 Sweden Apr. 1,1954

